Abstract:
The ,implementation of modern electronic and micro-processor
based control system has made the response of speed gov- '
ernors very fast. In this study we have shown the effect of
this type of governors on transient stability of a power systern.
The interconnected grid system of Bangladesh Power Development
Board is taken as a model for this study. The steady state
conditions prior to the fault are taken from the drawing no.
3754 N-7013 TO 03' studied by Lahmeyer International, GMBH. Lumping
all the generators operating in a power station to a single
unit, the set of swing equations for each equivalent.unit
are deduced consdering the effect of damper winding and speed
governors. In solving the swing equations, the variation of
shaft power with rotor speed is calculated from the equations
derived for speed control mechanism ,(governor). This derived
differential equations are represented in the form of a block
diagram.
To obtaine the power transfer between different pairs of
machines, the driving point and transfer admittances between
hypothetical machine internal-voltage-buses were calculated eliminating
all other nodes by matrix node elimination method. All
the loads were replaced by constant shunt addmittance between
!
the corresponding bus ill1dground. Swing equations were solved by
Runge -Kutta fourth order approximation method.
Three-phase short circuit of four different types covering
*-
major disturbances, such as generation rejection, load rejection
and loss of transmission facilities at four different
points were studied considering governor action and also neglecting
governor action. Each fault was studied with three different
modes of CB operations; (a) without autorecloser, (b) unsustained
fault and use of autorecloser and (c) sustained fault
and use of autorecloser. Taking Ghorasal-132 equivalent machines
as the reference the relative rotor angles of all the equivalent
machines were plotted by the computer.
The fOllowing facilities are available in the generalized
computer program developed for the proposed work:
(1) Determination of driving point and transfer admittance at
pre-fault, during fault and post-fault conditions.
(2) Determination of driving point and transfer impedances at
pre-fault, during fault and post fault conditions.
(3) Solution of the swing equations by Rungee-Kutta fourth
order approximation with or without governor action.
(4) Plotting of the swing curves.
This program can be used for any number of buses, generators,
and CB/Autorecloser time setting.
